Sports racquets, such as tennis rackets and racquetball racquets, have evolved with the objective of improving their strength to weight ratio. Originally made of wood, the frames of sports racquets later were made of aluminum alloy and now are mostly made of composite laminates of fiber and thermosetting organic resin. "Racquet", as used herein, encompasses racquetball racquets, tennis rackets, badminton racquets, squash racquets and any other sports implement that has a head which is strung with string or netting and which is designed to intercept and return a projectile.
In the most conventional sort of strung racquet, the striking area is defined by a head frame that is roughly oval in shape. Holes are made through the frame, typically in the plane of the strung area, for the passage of string therethrough. While this construction yields a desirably flat strung area without significant departures therefrom of the individual string segments, each string hole weakens the frame. It has been discovered that the most common impact failure mode of such racquets is a break in the frame at such a hole. Racquetball racquets, in particular, must exhibit considerable impact resistance because of their frequent contact, both inadvertent and intentional, of the walls and floor of the regulation racquetball court and other racquets.
Advances have also been made to improve the stiffness of the racquetball frame. One advance, used in a known badminton racquet, is to incorporate a structural fin which projects inwardly from the main frame member, itself usually formed as a tube having varying shapes or otherwise strengthened cross section. The fin in this badminton racquet is disposed inwardly around the entire circumference of the head frame and is used as an anchor for the string segments. In this embodiment, holes are made in the fin rather than in the tube. While this improves the strength of the tube, it is believed that if this design were used for racquetball or other racquet sports in which an elevated amount of equipment abuse occurs, other failure modes would arise: those of separation of the fin along its join with the head frame and the tearing out of the strings through the fins. To prevent this failure mode the fin would have to be increased in size and weight, with negative effects on playability.
Another conventional way to avoid frame-weakening holes is to wrap the string around the head using channels in the frame bumper for the purpose. This has the undesirable effects of introducing strings from the frame sides into the string bed at various angles to the general plane of the strung area and reducing the size of the flat portion of the strung bed. When a projectile such as a racquetball hits such a string in the vicinity of the frame, the projectile will be returned in an unanticipated direction, degrading playability. A need therefore persists in the sports racquet industry for racquets with improved strength to weight ratios and substantially flat strung areas.